<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      p {
        font-size: 20px;
      }
      p::first-letter {
        font-size: 40px;
      }
      p::first-line {
        color: springgreen;
      }
      p::selection {
        background-color: skyblue;
      }
      div::before {
        content: 'XXGG';
        color: blue;
      }
      div::after {
        content: 'GGXX';
      }

      /* 
        ::first-letter 首字母
        ::first-line 首行
        ::selection 选中区域
        ::before 元素的开始
        ::after 元素的结束
          before和after必须结合content属性使用
      */
    </style>
  </head>
  <body>
    <p>dsadsadasdsadsadasdadsa</p>
    <div>xlxllxlxlxxlxlxlxl</div>
  </body>
</html>
